1. Field of the Invention
The present invention relates a polyimide resin and a preparation method thereof and, more particularly, to a low temperature curable polyimide resin and a method of preparing the same.
2. Description of the Related Art
Recently, as the move for high integration, high density, high reliability, high speed, and the like, of electronic devices has been rapidly spreading in the field of semiconductor devices based on semiconductor and a liquid crystal display device, research into the use of the advantageous of an organic material easily available for processability, high purity, and the like, is actively ongoing.
In particular, a polyimide resin has many advantages that, besides its high heat resistance, excellent mechanical strength, low permittivity, high insulation characteristics, it has good polarization characteristics of a coated surface, has a very low content of impurity degrading the reliability of an element, and can be easily configured to have a fine form, so the use of a photosensitive insulating layer including a photosensitive resin including the polyimide resin is extending even to a display sector.
In order to synthesize polyimide, generally, a diamine component and a dianhydride component are polymerized in a polar organic solvent such as N-methyl-2-pyrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF) through 2-stage condensation polymerization to obtain a polyimide precursor solution, and the obtained polyimide precursor solution is coated on silicon wafer, glass, or the like, and then thermally treated at a high temperature so as to be cured (or hardened).
A commercialized polyimide product for an electronic material is supplied in a state of a polyimide precursor solution or a polyimide film, and in the field of a semiconductor device, the polyimide produce is largely supplied in the state of a polyimide precursor solution.
However, the method of preparing the polyimide polymer requires a high curing temperature (i.e., 300° C. or higher), having a problem in that it cannot be used for a process vulnerable to heat. In addition, although the polyimide precursor solution undergoes the high temperature curing operation, it cannot be completely changed into polyimide.
Thus, in an effort to solve this problem, a polymerization method of performing chemical imidizing in a liquid state by using a catalyst has been developed; however, this method also uses a high boiling point solvent as well as it requires the high temperature process, so after the polymerization process, the high temperature curing process must be performed again in order to remove the solvent.
In addition, when a high temperature thermal treatment is intended to be performed to prepare the polyimide resin, large-scale heat equipment is required to enhance production efficiency.